Provided is an optically anisotropic layer having an excellent surface condition, with which an image display device having an excellent contrast can be manufactured; and an optical film, a polarizing plate, and an image display device, each having the optically anisotropic layer. The optically anisotropic layer is obtained by immobilizing a polymerizable liquid crystal composition including a polymerizable rod-shaped liquid crystal compound exhibiting a liquid crystal state of a smectic phase and an additive in a liquid crystal state of a smectic phase, in which a molecular length A (Å) of the polymerizable rod-shaped liquid crystal compound, a layer interval B (Å) of the smectic phase of the optically anisotropic layer, and a molecular length C (Å) of the additive satisfy a relationship of Expression (1-1), 0.5×B≤C≤0.6×A . . . (1-1).